When Nat, her best friend Jess and singing-star wannabe Harper sing together, their harmonies bring down the house. For Nat, the experience sparks a driving new desire to perform. But when the girls form a trio and enter a contest for a chance to play at the Tall Grass Music Festival, Nat finds that harmony--musical and otherwise--is hard to maintain. Her bandmates almost never agree, her new boyfriend starts behaving more like a non-boyfriend, and the trio's famous-musician mentor doesn't even like the way Nat breathes. Every day, Nat's dream of performing at Tall Grass seems farther away,...